Abstract
Respiratory-type flows facilitate the exchange of fluid through an orifice in many natural and engineered environments. The external flow dynamics for an idealized respiratory-type flow, consisting of periodic inhalation and exhalation of a fixed tidal volume of fluid through a circular orifice at the end of a tube, are investigated. In both numerical and experimental investigations, inertial effects produce asymmetric inhalant and exhalant flow structures, resulting in a dynamic exchange of fluid volume across the orifice. A Lagrangian approach is used to quantify the reinhalation ratio , defined as the amount of exhaled fluid that is subsequently reinhaled. Results show that these flow structure asymmetries and hence are strongly sensitive to Reynolds number, and, to a lesser extent, Womersley number or Strouhal number. At low Reynolds number, where viscous effects dominate, we observe flow kinematics similar to an ideal source or sink and the exchange ratio asymptotes to an upper limit. As the inertial effects become more dominant with increasing Reynolds number, we instead observe jetlike flow structures and a rapid decrease in . In the context of biological sensory and metabolic processes, these results suggest organisms can optimize the exchange of fluid with surrounding environment by modulating the asymmetries in the flow structures arising during olfactory and respiratory activity.
7 More- Received 20 May 2020
- Accepted 21 August 2020
DOI:https://doi.org/10.1103/PhysRevFluids.5.093103
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